1. Field of the Invention
The present invention relates to the electrolytic reduction and separation of europium values, together with an electrolysis cell for conducting such electrolytic reduction/separation.
2. Description of the Prior Art
Europium is a rare earth element, the content of which in a variety of minerals is typically quite low compared to that of the other rare earths. On the other hand, its applications, in particular in respect of the luminescence thereof, require a high degree of purity. Consequently, for this particular element there exists a dual problem of separation and purification.
Generally, the production of europium entails processes in which, in a first stage thereof, a reduction of europium (III) to europium (II) is carried out, and, in a second stage, a chemical treatment is carried out exhibiting a high degree of specificity relative to europium.
More precisely, such process is carried out as follows. The initial material is usually a solution of rare earth chlorides, which solution is subjected to treatment through a zinc or zinc amalgam column (Jones column). The europous sulfate is then precipitated from the solution thus treated by the addition of sulfate ions.
Such a process has a number of disadvantages.
First, it lacks flexibility. Further, zinc and mercury are transferred into solution. Zinc interferes with the subsequent separations of the rare earths and the mother liquors of the Jones column must be subjected to a specific mercury depollution treatment.
Finally, the yields and resulting purities are inadequate.
Electrolytic processes too have been proposed for the reduction of europium values. However, the degrees of conversion and faradic yields are characteristically insufficient.